Importance of Freshwater Mussels for Water Quality in the Tidal Delaware River

Delaware Estuary Science & Environmental Summit

January 29, 2013

Danielle Kreeger, Melanie Mills, Lance Butler, Priscilla Cole, and Roger Thomas

Headwaters

to Ocean

Shellfish

Restoration

1. Non-tidal

2. Intertidal

3. Subtidal

1 2

3

CTUIR Freshwater Mussel Project

Nature’s Benefits

Bivalve Shellfish are “Ecosystem Engineers”

Kreeger

Oyster Reefs

Mussel Beds

Start

8 adult mussels No mussels

Biofiltration Potential

Slide from Dick Neves, VA Tech

Later

8 adult mussels No mussels

Slide from Dick Neves, VA Tech

Biofiltration Potential

•

1919 Since

1996

Kreeger

2012

Scientific Name Scientific Name DE NJ PA

ALASMIDONTA HETERODON DWARF WEDGEMUSSEL Endangered Endangered Critically Imperiled

ALASMIDONTA UNDULATA TRIANGLE FLOATER Extirpated ? Threatened Vulnerable

ALASMIDONTA VARICOSA BROOK FLOATER Endangered Endangered Imperiled

ANODONTA IMPLICATA ALEWIFE FLOATER Extremely Rare no data Extirpated ?

ELLIPTIO COMPLANATA EASTERN ELLIPTIO common common Secure

LAMPSILIS CARIOSA YELLOW LAMPMUSSEL Endangered Threatened Vulnerable

LAMPSILIS RADIATA EASTERN LAMPMUSSEL Endangered Threatened Imperiled

LASMIGONA SUBVIRIDIS GREEN FLOATER no data Endangered Imperiled

LEPTODEA OCHRACEA TIDEWATER MUCKET Endangered Threatened Extirpated ?

LIGUMIA NASUTA EASTERN PONDMUSSEL Endangered Threatened Critically Imperiled

MARGARITIFERA MARGARITIFERA EASTERN PEARLSHELL no data no data Imperiled

PYGANODON CATARACTA EASTERN FLOATER no data no data Vulnerable

STROPHITUS UNDULATUS SQUAWFOOT Extremely Rare Species of Concern Apparently Secure

State Conservation Status

Patchy, Impaired Extirpated Rare

Delaware River Basin

Freshwater Mussel Discoveries Tidal Delaware River:

Lots of animals 7 Species

Genetically Appropriate

Promise for Restoration

Questions:

How many mussels exist here?

How much water do they filter?

What happens to filtered material?

Do current populations benefit water quality?

Can mussel restoration improve water quality?

To Understand EcoServices, Need…

Physiology

Population Surveys

Ecology

Monitoring, Variability

Kreeger

Surveys

Determine current

mussel population

status

Identify sources for

restoration

Areas with Mussels:

Prioritize for

Conservation

Areas without Mussels:

Prioritize for

Restoration

Qualitative vs. Quantitative Surveys

Qualitative: • Opportunistic methods • Timed searches • Data on presence/absence, catch per unit effort • Assess large areas • Most common, cost effective Quantitative: • Intensive methods • Transects and quadrats • Data on densities, sizes, richness • Smaller areas • Rare, more costly Only way to assess ecosystem benefits

2012 Quantitative Surveys

Goals:

1. Quantify mussel species richness and density

2. Examine relationships with: • Depth (see Mills poster)

• Substrate (see Butler talk)

3. Estimate Potential Water Filtration per Bed

Tidal Delaware River

Shallow Subtidal Shorelines

Native Mussel Assemblages

Sample substrate

Methods

Four Sites

Shallow subtidal zone (0-8 feet below mean low water)

Transects: 8 per site

Quadrats: 3-4 per transect,

stratified by depth

Quadrat = 1m2 steel frame

Set up transects

Collect mussels

Haul to shore

Quadrat searches

Measure and ID

RTK GPS

Maps

Site 1

• Four mussel species

• Richness = 1.4 species m-2

• Density:

range = 0 – 29 mussels m-2

mean = 5.5 mussels m-2

See Mills and Butler presentations for depth and substrate

relationships, respectively

Pyganodon

cataracta Elliptio

complanata

Site 2

• Six mussel species

• Richness = 3.4 species m-2

• Density:

range = 0 – 80 mussels m-2

mean = 30.1 mussels m-2

See Mills and Butler presentations for depth and substrate

relationships, respectively

Pyganodon

cataracta Elliptio

complanata

Site 2

See Mills poster

Site 3

• Five mussel species

• Richness = 2.4 species m-2

• Density:

range = 0 – 129 mussels m-2

mean = 17.6 mussels m-2

See Mills and Butler presentations for depth and substrate

relationships, respectively

Elliptio

complanata

Site 4

• Five mussel species

• Richness = 2.4 species m-2

• Density:

range = 0 – 64 mussels m-2

mean = 10.8 mussels m-2

See Mills and Butler presentations for depth and substrate

relationships, respectively

Elliptio

complanata

How much do they weigh? No animals sacrificed in 2012

Dry tissue weights estimated from from earlier studies

11 species of freshwater mussels

653 animals (harvested 2000-2011)

LOG(ShellLength) = 4.22566 + 0.322226*LOG(DTW)

-4.6 -2.6 -0.6 1.4 3.4

LOG(DTW)

2.7

3.1

3.5

3.9

4.3

4.7

5.1

LO

G(S

hell

Len

gth

)

R2 = 80.0%

Species-specific weight estimates

sci_nameActinonaias ligamentinaAnodonta californianusAnodonta oregonensisElliptio complanataElliptio dilitataGonidea angulataLampsilis cariosaLeptodea ochraceaLigumia nasutaMargaratifera falcataPyganodon cataracta

Plot of Fitted Model

-4.6 -2.6 -0.6 1.4 3.4

LOG(DTW)

2.7

3.1

3.5

3.9

4.3

4.7

5.1L

OG

(Sh

ellL

en

gth

)sci_name

Actinonaias ligamentinaAnodonta californianusAnodonta oregonensisElliptio complanataElliptio dilitataGonidea angulataLampsilis cariosaLeptodea ochraceaLigumia nasutaMargaratifera falcataPyganodon cataracta

Plot of Fitted Model

-4.6 -2.6 -0.6 1.4 3.4

LOG(DTW)

2.7

3.1

3.5

3.9

4.3

4.7

5.1

LO

G(S

hellL

en

gth

)

R2 = 85.9%

Valu

e p

er

m2 (

mean %

±S

E)

Density (#)

Dry Tissue Weight (g)

0

10

20

30

40

50

60

70

80

90

Site 1

Site 2

Site 3

Site 4

C n=12 n=30BCB

A

a

bbb

Mussel Density and Total Weight by Site

Gra

ms / M

ussel

(mean ±

SE

)

Dry Tissue Weight / Density

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Site 1

Site 2

Site 3

Site 4

A

B

B

A

Mussel Size by Site

Other Findings Species richness was positively related to density

Rarest species was Ligumia nasuta, eastern pondmussel – healthy size range from juveniles to old adults

Tidewater muckets were abundant

Juvenile mussels were abundant at 2 of 4 sites, suggesting reproduction is occuring

Plot of Fitted Model

Richness = 0.948775 + 0.816763*LOG(Density)

0 1 2 3 4 5

LOG(Density)

0

1

2

3

4

5

6

Ric

hn

ess

R2 = 67.3%

Total Mussel Population Size

Densities Extrapolated to Survey Areas

Quads (n)

Mussels per Quad (# m-2) Survey Area (m2)

Mussel Number

Average Std. Error (pooled)

Site 1 21 5.5 4.4 4,230 23,163

Site 2 27 30.1 3.9 9,504 286,175

Site 3 24 17.6 4.1 13,983 245,863

Site 4 24 10.8 4.1 10,658 115,458

4 Bed Totals> 96 16.8 38,375 670,660

2012 Abundance Surveys

Estimated Population Biomass per Site

Quads (n)

Mussels per Quad (# m-2)

Dry Tissue Weight per Quad (g m-2)

Survey Area (m2)

Mussel Number

Mussel Tissue Dry Weight

Average Std. Error (pooled) Average

Std. Error (pooled)

(g)

Site 1 21 5.5 4.4 17.5 8.8 4,230 23,163 74,210

Site 2 27 30.1 3.9 76.0 7.8 9,504 286,175 722,145

Site 3 24 17.6 4.1 16.5 8.3 13,983 245,863 230,725

Site 4 24 10.8 4.1 9.8 8.3 10,658 115,458 104,226

4 Bed Totals> 96 16.8 31.8 38,375 670,660 1,131,307

How much do they filter?

Apply Existing Clearance Rate Data

Lab Studies Field Studies

Kreeger

Review in Progress for Chesapeake Executive Order Study

Number of Species Diet

Clearance Rate

(L h-1 g-1)

Kryger and Riisgard (1988) 4 lab algae 1.11

Pusch et al. (2001) 2 field seston 0.38

Gatenby (2000) 3 lab algae 1.72

Silverman et al. (1995, 1997) 5 lab bacteria 0.77

Patterson (1984) 1 lab algae 0.38

Vanderploeg et al. (1995) 1 lab algae 1.45

Gatenby & Kreeger (2003) 6 field seston, lab algae 0.23

Kreeger (2011) 3 field seston 0.96

Mean > 0.875

Estimated Water Filtration

Quads (n)

Mussels per Quad (# m-2)

Dry Tissue Weight per Quad (g m-2)

Survey Area (m2)

Mussel Number

Mussel Tissue Dry

Weight

Typical Clearance

Rate

Typical Clearance

Rate

Bed Clearance Rate

Typical TSS Filtration

Average Std. Error (pooled) Average

Std. Error (pooled)

(g) (L hr-1 g DTW-1)

(gal day-1 g DTW-1)

(gal day-1) (metric tons

DW day-1)

Site 1 21 5.5 4.4 17.5 8.8 4,230 23,163 74,210

0.875 5.55

411,867 0.54

Site 2 27 30.1 3.9 76.0 7.8 9,504 286,175 722,145 4,007,906 5.29

Site 3 24 17.6 4.1 16.5 8.3 13,983 245,863 230,725 1,280,524 1.69

Site 4 24 10.8 4.1 9.8 8.3 10,658 115,458 104,226 578,456 0.76

4 Bed Totals> 96 16.8 31.8 38,375 670,660 1,131,307 6,278,754 8.29

Observations

Potential filtration of 6.3 million gallons per day for these 4 beds is: 2.5% of freshwater inflow from the Delaware River; and 1.6% of drinking water withdrawals for Philadelphia

Estimated suspended solids removal of 8.3 metric tons per day is: 121 times that by mussels in 6-mile reach of Brandywine River

More beds exist, especially in New Jersey

Study is limited to shallow subtidal shorelines, mussel densities increased with depth to limit of sampling

Water processing potential may not reflect actual water filtration

Many expected suitable sites had few or no mussels, especially where bed stability appeared compromised; habitat restoration would benefit mussel populations and ranges

Summary • Freshwater mussels are the most imperiled animals nationally

and locally

• Current freshwater mussel populations in the tidal Delaware

River are abundant enough to measurably help sustain water

quality

• For these reasons, critical habitat for mussels needs to be

mapped and protected

• Populations are far below historic levels basin-wide, and

mussel restoration would promote water quality and other

benefits

• More research is needed on physiological ecology of mussels

identify fates of filtered material and improve ecosystem service

models

Thanks to Our Funder: Pennsylvania Coastal Zone Management Program

www.DelawareEstuary.org

Extra Slides

DRBC

Desired Watershed Condition: A diverse and robust assemblage of native bivalves living in abundance in all available tidal and non-tidal ecological niches and providing maximum possible natural benefits.

Kreeger

>60 Species of Bivalves in the Delaware Estuary Watershed

DRBC

Crassostrea virginica

Elliptio complanata

Geukensia demissa

11 Other Species of Freshwater Unionid Mussels

Mya arenaria

Rangia cuneata

Corbicula fluminea

Mytilus edulis

Ensis directus

Mercenaria mercenaria

Freshwater Mussel Recovery Program 1. Surveys

• Establish current range and density for historically present species • Identify candidate areas to be conserved and/or restored • Qualitative (rapid) and Quantitative (intensive) • Delineate critical habitat to be protected

2. Restoration Suitability Tests • Assess if candidate restoration sites can sustain healthy mussel assemblages

3. Reintroduction • Transplant gravid broodstock from healthy extant populations nearby • Monitor success

4. Propagation • Produce genetically appropriate seed mussels in hatcheries for restocking

5. Education • Build awareness for mussel conservation and holistic restoration

6. Promote Habitat and Water Quality Improvement (e.g. dam removal)

Freshwater Mussel Recovery Program

0

200400

600800

1,0001,200

1,4001,600

1,8002,000

Millions of

Liters

Processed

1 2 4 6 8 10 15 30

Years After Planting

Series1

Not including progeny

Goals Based on Ecosystem Services